Comparative Analysis of 5-Year Clinical Outcomes and Patterns of Failure of Proton Beam Therapy Versus Intensity Modulated Radiation therapy for Prostate Cancer in the Postoperative Setting

Abstract

Although proton beam therapy (PBT) is a rapidly expanding modality to treat prostate cancer compared with intensity modulated radiation therapy (IMRT), data comparing disease control outcomes and patterns of failure in the postprostatectomy setting remain substantially limited. Methods and Materials: All patients who underwent postoperative IMRT or PBT to the prostate bed only at a single institution were included (2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017). Endpoints included biochemical failure (BF; using institutional and recent cooperative group trial definitions), local failure (LF), regional failure (RF), distant failure (DF), and all-cause mortality. A case-matched cohort analysis was performed using 3-to-1 nearest-neighbor matching; multivariable Cox proportional hazards modeling (MVA) estimated hazard ratios for diseaserelated outcomes by treatment modality. Results: Of 295 men, 260 were matched (n Z 65 PBT, 195 IMRT); after matching, only age at diagnosis (P < .01) significantly differed between cohorts. At a median follow-up of 59 months, BF (institution-defined), LF, RF, DF, and mortality rates were 45% (n Z 29), 2% (n Z 1), 9% (n Z 6), 9% (n Z 6), and 2% (n Z 1) for PBT, and 41% (n Z 80), 3% (n Z 5), 7% (n Z 13), 9% (n Z 18), and 5% (n Z 9) for IMRT (all P > .05). RT modality was not significantly associated with BF on MVA using institutional or cooperative group definitions (all P > .05), nor with LF (P Z .82), RF (P Z .11), DF (P Z .36), or all-cause mortality (P Z .69). Patterns of failure were qualitatively similar between cohorts (DF: bone, retroperitoneal nodes, lung).

Does particle radiation have superior radiobiological advantages for prostate cancer cells? A systematic review of in vitro studies

“…Charged particle therapy (CPT) for PCa gained increasing attention in the past decade because of its superior physical and biological properties. Several studies have shown a reduced radiation toxicity, lower risk of secondary primary tumor and an improved biochemical-free survival (also known as biochemical disease-free survival) compared with IMRT [5][6][7][8][9][10][11][12][13][14]. In these studies, despite the lack of high-quality randomized controlled trials, existing data suggested that CPT exhibited great potential for sparing normal tissue as well as excellent overall survival rate and local control rate [15].…”